MicroRNA Expression Prior to Biting in a Vector Mosquito Anticipates Physiological Processes Related to Energy Utilization, Reproduction and Immunity

Understanding the molecular and physiological processes underlying biting behavior in vector mosquitoes has important implications for developing novel strategies to suppress disease transmission. Here, we conduct small-RNA sequencing and qRT-PCR to identify differentially expressed microRNAs (miRNAs) in the head tissues of two subspecies of Culex pipiens that differ in biting behavior and the ability to produce eggs without blood feeding. We identified eight differentially expressed miRNAs between biting C. pipiens pipiens (Pipiens) and non-biting C. pipiens molestus (Molestus); six of these miRNAs have validated functions or predicted targets related to energy utilization (miR8-5-p, miR-283, miR-2952-3p, miR-1891), reproduction (miR-1891), and immunity (miR-2934-3p, miR-92a, miR8-5-p). Although miRNAs regulating physiological processes associated with blood feeding have previously been shown to be differentially expressed in response to a blood meal, our results are the first to demonstrate differential miRNA expression in anticipation of a blood meal before blood is actually imbibed. We compare our current miRNA results to three previous studies of differential messenger RNA expression in the head tissues of mosquitoes. Taken together, the combined results consistently show that biting mosquitoes commit to specific physiological processes in anticipation of a blood meal, while non-biting mosquitoes mitigate these anticipatory costs.

Tandem spawning and development in the African freshwater pufferfish Tetraodon schoutedeni

To advance breeding techniques for the African freshwater pufferfish Tetraodon schoutedeni and observe tandem spawning closely, we monitored the reproduction of captive individuals. Eight spawning sessions (stable water temperature 24-25°C; daily light period 07:00-19:00) occurred between May 2016 and November 2017. After 65-150 min of tandem swimming (the male biting and clinging to the female's abdomen), 3-50 spherical, weakly adhesive eggs were spawned, being scattered onto the sandy substrate or water plants. The removal of cohabitants (potentially eating spawned eggs) and provision of small initial food items, such as small-type Brachionus spp., for larval fish were essential for successful breeding.

Biting Fibroma of the Lower Lip: A Case Report and Literature Review on an Irritation Fibroma Occurring at the Traumatic Site of a Tooth Bite

Biting fibroma, an irritation fibroma or traumatic fibroma associated with a history of a prior lesion-related tooth bite or biting injury at the site, is a commonly acquired benign reactive lesion of the oral cavity. It is usually an asymptomatic, small, mucosa-colored, smooth, pedunculated or sessile papule. A biting fibroma is most commonly located on the buccal mucosa, followed by, in decreasing frequency, on the tongue or lip or hard palate or gingiva. It typically presents as a solitary lesion; however, it can appear as multiple lesions. Excision is the treatment of choice for a biting fibroma; however, the resolution of the lesion-associated chronic inflammation is also necessary to prevent a recurrence. The clinical history, lesion morphology, and pathology findings of an illustrative patient with a biting fibroma were included in this case report. An 80-year-old woman was described who developed a biting fibroma at the site of a tooth bite on her lower lip. An excisional biopsy not only confirmed the suspected diagnosis of a biting fibroma but also successfully treated her condition by removing the lesion; there was no recurrence. In conclusion, the diagnosis of a biting fibroma should be considered when a patient presents with a new intraoral lesion, particularly if associated with an acute injury or chronic inflammation of the site. Since the clinical differential diagnosis of a biting fibroma includes various other benign conditions and less common malignant neoplasms, a biopsy that removes the lesion may not only establish the diagnosis but also potentially provide adequate treatment.

Biomechanical Modelling for Tooth Survival Studies: Mechanical Properties, Loads and Boundary Conditions-A Narrative Review

Recent biomechanical studies have focused on studying the response of teeth before and after different treatments under functional and parafunctional loads. These studies often involve experimental and/or finite element analysis (FEA). Current loading and boundary conditions may not entirely represent the real condition of the tooth in clinical situations. The importance of homogenizing both sample characterization and boundary conditions definition for future dental biomechanical studies is highlighted. The mechanical properties of dental structural tissues are presented, along with the effect of functional and parafunctional loads and other environmental and biological parameters that may influence tooth survival. A range of values for Young's modulus, Poisson ratio, compressive strength, threshold stress intensity factor and fracture toughness are provided for enamel and dentin; as well as Young's modulus and Poisson ratio for the PDL, trabecular and cortical bone. Angles, loading magnitude and frequency are provided for functional and parafunctional loads. The environmental and physiological conditions (age, gender, tooth, humidity, etc.), that may influence tooth survival are also discussed. Oversimplifications of biomechanical models could end up in results that divert from the natural behavior of teeth. Experimental validation models with close-to-reality boundary conditions should be developed to compare the validity of simplified models.

Comparative examination of pinniped craniofacial musculature and its role in aquatic feeding

Secondarily aquatic tetrapods have many unique morphologic adaptations for life underwater compared with their terrestrial counterparts. A key innovation during the land-to-water transition was feeding. Pinnipeds, a clade of air-breathing marine carnivorans that include seals, sea lions, and walruses, have evolved multiple strategies for aquatic feeding (e.g., biting, suction feeding). Numerous studies have examined the pinniped skull and dental specializations for underwater feeding. However, data on the pinniped craniofacial musculoskeletal system and its role in aquatic feeding are rare. Therefore, the objectives of this study were to conduct a comparative analysis of pinniped craniofacial musculature and examine the function of the craniofacial musculature in facilitating different aquatic feeding strategies. We performed anatomic dissections of 35 specimens across six pinniped species. We describe 32 pinniped craniofacial muscles-including facial expression, mastication, tongue, hyoid, and soft palate muscles. Pinnipeds broadly conform to mammalian patterns of craniofacial muscle morphology. Pinnipeds also exhibit unique musculoskeletal morphologies-in muscle position, attachments, and size-that likely represent adaptations for different aquatic feeding strategies. Suction feeding specialists (bearded and northern elephant seals) have a significantly larger masseter than biters. Further, northern elephant seals have large and unique tongue and hyoid muscle morphologies compared with other pinniped species. These morphologic changes likely help generate and withstand suction pressures necessary for drawing water and prey into the mouth. In contrast, biting taxa (California sea lions, harbor, ringed, and Weddell seals) do not exhibit consistent craniofacial musculoskeletal adaptations that differentiate them from suction feeders. Generally, we discover that all pinnipeds have well-developed and robust craniofacial musculature. Pinniped head musculature plays an important role in facilitating different aquatic feeding strategies. Together with behavioral and kinematic studies, our data suggest that pinnipeds' robust facial morphology allows animals to switch feeding strategies depending on the environmental context-a critical skill in a heterogeneous and rapidly changing underwater habitat.

Work that body: fin and body movements determine herbivore feeding performance within the natural reef environment

Herbivorous fishes form a keystone component of reef ecosystems, yet the functional mechanisms underlying their feeding performance are poorly understood. In water, gravity is counter-balanced by buoyancy, hence fish are recoiled backwards after every bite they take from the substrate. To overcome this recoil and maintain contact with the algae covered substrate, fish need to generate thrust while feeding. However, the locomotory performance of reef herbivores in the context of feeding has hitherto been ignored. We used a three-dimensional high-speed video system to track mouth and body kinematics during in situ feeding strikes of fishes in the genus Zebrasoma, while synchronously recording the forces exerted on the substrate. These herbivores committed stereotypic and coordinated body and fin movements when feeding off the substrate and these movements determined algal biomass removed. Specifically, the speed of rapidly backing away from the substrate was associated with the magnitude of the pull force and the biomass of algae removed from the substrate per feeding bout. Our new framework for measuring biting performance in situ demonstrates that coordinated movements of the body and fins play a crucial role in herbivore foraging performance and may explain major axes of body and fin shape diversification across reef herbivore guilds.

Does Diversity Matter? Behavioural Differences between Piglets Given Diverse or Similar Forms of Enrichment Pre-Weaning

Simple Summary

This study looked at behavioural differences between piglets provided with either two identical or two different enrichment materials. From seven days-old until weaning, piglets were given hessian fabrics or bamboo: the control group had only hessian, and the diverse groups had both hessian and bamboo. One object was attached to the pen wall and the other suspended in the middle of the pen and piglets behaviours were observed. Objects suspended in the middle of the pen attracted more attention than objects attached to the wall. Piglets preferred hessian over bamboo, and the interest in hessian increased over time, while interest in bamboo remained unchanged. Piglets interacted differently with the objects: more oral manipulation and shaking occurred with the hessian and more pushing occurred with the bamboo. Control piglets performed more biting than piglets with diverse enrichment, both pre- and post-weaning. Therefore, providing different forms of enrichment to piglets pre-weaning has the potential to reduce biting occurrences and, thus, to promote welfare. Hessian was probably favoured because it allowed oral manipulation, which was the most frequent interaction observed.

Abstract

This study investigated the behavioural effects of providing different enrichment materials to suckling piglets from 7 days-old until weaning. One object was attached to the pen wall (WALL), and the other was suspended in the middle of the pen (MID). Control group had the hessian fabric in both locations, and the two diverse groups had hessian and bamboo stick in alternate locations (i.e., BMID-HWALL and HMID-BWALL). Piglets behaviour was recorded on D0 (object introduction), D1, D5, D8, D12, and D14; at weaning and 1, 3, 5 and 15 days after. Groups did not differ in approaching or interacting with objects on D0. MID objects attracted more attention than WALL objects (p < 0.01). Piglets interacted more with hessian than bamboo (p < 0.001). They performed more oral manipulation and shaking with hessian (p < 0.001), but more pushing of bamboo (p < 0.001). Interactions with objects increased with time (p < 0.001), especially with hessian (p < 0.01), while interest in bamboo remained unchanged. Control piglets performed more biting than piglets with diverse enrichment (pooled data), both pre- and post-weaning (p < 0.05). Therefore, providing different types of enrichment material can reduce biting behaviour pre- and post-weaning. Hessian was favoured, possibly because this was easier to bite and shake, which were the behaviours most often observed.

Masticatory Apparatus Performance and Functional Morphology in the Extremely Large Mice from Gough Island

Since their arrival approximately 200 years ago, the house mice (Mus musculus) on Gough Island (GI) rapidly increased in size to become the largest wild house mice on record. Along with this extreme increase in body size, GI mice adopted a predatory diet, consuming significant quantities of seabird chicks and eggs. We studied this natural experiment to determine how evolution of extreme size and a novel diet impacted masticatory apparatus performance and functional morphology in these mice. We measured maximum bite force and jaw opening (i.e., gape) along with several musculoskeletal dimensions functionally linked to these performance measurements to test the hypotheses that GI mice evolved larger bite forces and jaw gapes as part of their extreme increase in size and/or novel diet. GI mice can bite more forcefully and open their jaws wider than a representative mainland strain of house mice. Similarly, GI mice have musculoskeletal features of the masticatory apparatus that are absolutely larger than WSB mice. However, when considered relative to body size or jaw length, as a relevant mechanical standard, GI mice show reduced performance, suggesting a size-related decrease in these abilities. Correspondingly, most musculoskeletal features are not relatively larger in GI mice. Incisor biting leverage and condylar dimensions are exceptions, suggesting relative increases in biting efficiency and condylar rotation in GI mice. Based on these results, we hypothesize that evolutionary enhancements in masticatory performance are correlated with the extreme increase in body size and associated musculoskeletal phenotypes in Gough Island mice. Anat Rec, 2019. © 2018 American Association for Anatomy.

Commentary: A review of risk of hepatitis B and C transmission through biting or spitting

A draft UK Parliamentary Bill sought to criminalize assaults on emergency workers through biting and spitting. This seemed to be based on a fear of bloodborne virus transmission. We undertook a literature search to clarify the risk of hepatitis infection from such exposures. We identified 245 possible papers and then reduced these to those relevant to HBV and HCV transmission through biting or spitting and the scientific plausibility. Nine papers were identified, reporting 16 possible cases of HBV (15 bites, 1 spitting) and 2 of HCV transmission (both bites). Only 3 HBV transmissions by bites and 1 by spitting and both HCV transmissions were felt to be plausible. Although both HBV DNA and HCV RNA can be found in the saliva of infected patients, it seems unlikely that there is enough to transmit infection unless there is blood contamination. In conclusion, the risk of acquiring HCV through spitting is negligible and is very low for HBV. The risk is also low for acquiring HBV and HCV through biting, especially if no blood is apparent in the saliva.

Effect of Jaw Clenching on Balance Recovery: Dynamic Stability and Lower Extremity Joint Kinematics after Forward Loss of Balance

Postural control is crucial for most tasks of daily living, delineating postural orientation and balance, with its main goal of fall prevention. Nevertheless, falls are common events, and have been associated with deficits in muscle strength and dynamic postural stability. Recent studies reported on improvements in rate of force development and static postural control evoked by jaw clenching activities, potentially induced by facilitation of human motor system excitability. However, there are no studies describing the effects on dynamic stability. The present study, therefore, aimed to investigate the effects of submaximum jaw clenching on recovery behavior from forward loss of balance. Participants were 12 healthy young adults, who were instructed to recover balance from a simulated forward fall by taking a single step while either biting at a submaximum force or keeping the mandible at rest. Bite forces were measured by means of hydrostatic splints, whereas a 3D motion capture system was used to analyze spatiotemporal parameters and joint angles, respectively. Additionally, dynamic stability was quantified by the extrapolated CoM concept, designed to determine postural stability in dynamic situations. Paired t-tests revealed that submaximum biting did not significantly influence recovery behavior with respect to any variable under investigation. Therefore, reductions in postural sway evoked by submaximum biting are obviously not transferable to balance recovery as it was assessed in the present study. It is suggested that these contradictions are the result of different motor demands associated with the abovementioned tasks. Furthermore, floor effects and the sample size might be discussed as potential reasons for the absence of significances. Notwithstanding this, the present study also revealed that bite forces under both conditions significantly increased from subjects’ release to touchdown of the recovery limb. Clenching the jaw, hence, seems to be part of a common physiological repertoire used to improve motor performance.

Proximate determinants of bite force in Anolis lizards

Performance measures associated with the vertebrate jaw system may provide important insights into vertebrate ecology and evolution because of their importance in many ecologically relevant tasks. Previous studies have shown that in many taxa, evolution toward higher bite force has gone hand in hand with the evolution of larger body size. However, independent of differences in overall body size, bite force may vary depending on head size and shape as well. Moreover, the underlying musculature may also drive variation in bite force. Here, we investigate the proximate determinants of bite force in lizards of the genus Anolis. We dissected the jaw muscles and quantified muscle mass, fibre length, and cross-sectional area. Data were analysed for both sexes independently given the sexual dimorphism detected in the dataset. Our results show that the traits that explain bite force are similar in both males and females with overall body size and muscle mass being the principal determinants. Among the different muscles examined, the adductor externus and the pseudotemporalis groups were the best determinants of bite force. However, models run for males predicted the variation in bite force better than models for females, suggesting that selection on morphology improving bite force may be stronger in males.

The effect of oral motor activity on the athletic performance of professional golfers

Human motor control is based on complex sensorimotor processes. Recent research has shown that neuromuscular activity of the craniomandibular system (CMS) might affect human motor control. In particular, improvements in postural stability and muscle strength have been observed as a result of voluntary jaw clenching. Potential benefits of jaw aligning appliances on muscle strength and golf performance have also been described. These reports are highly contradictory, however, and the oral motor task performed is often unclear. The purpose of our study was, therefore, to investigate the effect of submaximum biting on golf performance via shot precision and shot length over three different distances. Participants were 14 male professional golfers - seven with sleep bruxism and seven without - randomly performing golf shots over 60m, 160m, or driving distance while either biting on an oral splint or biting on their teeth; habitual jaw position served as the control condition. Statistical analysis revealed that oral motor activity did not systematically affect golf performance in respect of shot precision or shot length for 60m, 160 m, or driving distance. These findings were reinforced by impact variables such as club head speed and ball speed, which were also not indicative of significant effects. The results thus showed that the strength improvements and stabilizing effects described previously are, apparently, not transferable to such coordination-demanding sports as golf. This could be due to the divergent motor demands associated with postural control and muscle strength on the one hand and the complex coordination of a golf swing on the other. Interestingly, subjects without sleep bruxism performed significantly better at the short distance (60 m) than those with bruxism. Because of the multifactorial etiology of parafunctional CMS activity, conclusions about the need for dental treatment to improve sports performance are, however, completely unwarranted.

Force-controlled biting alters postural control in bipedal and unipedal stance

Human posture is characterised by inherent body sway which forces the sensory and motor systems to counter the destabilising oscillations. Although the potential of biting to increase postural stability has recently been reported, the mechanisms by which the craniomandibular system (CMS) and the motor systems for human postural control are functionally coupled are not yet fully understood. The purpose of our study was, therefore, to investigate the effect of submaximum biting on postural stability and on the kinematics of the trunk and head. Twelve healthy young adults performed force-controlled biting (FB) and non-biting (NB) during bipedal narrow stance and single-leg stance. Postural stability was quantified on the basis of centre of pressure (COP) displacements, detected by use of a force platform. Trunk and head kinematics were investigated by biomechanical motion analysis, and bite forces were measured using a hydrostatic system. The results revealed that FB significantly improved postural control in terms of reduced COP displacements, providing additional evidence for the functional coupling of the CMS and human posture. Our study also showed, for the first time, that reductions in the sway of the COP were accompanied by reduced trunk and head oscillations, which might be attributable to enhanced trunk stiffness during FB. This physiological response to isometric activation of the masticatory muscles raises questions about the potential of oral motor activity as a strategy to reduce the risk of falls among the elderly or among patients with compromised postural control.

Does shape co-variation between the skull and the mandible have functional consequences? A 3D approach for a 3D problem

Morpho-functional patterns are important drivers of phenotypic diversity given their importance in a fitness-related context. Although modularity of the mandible and skull has been studied extensively in mammals, few studies have explored shape co-variation between these two structures. Despite being developmentally independent, the skull and mandible form a functionally integrated unit. In the present paper we use 3D surface geometric morphometric methods allowing us to explore the form of both skull and mandible in its 3D complexity using the greater white-toothed shrew as a model. This approach allows an accurate 3D description of zones devoid of anatomical landmarks that are functionally important. Two-block partial least-squares approaches were used to describe the co-variation of form between skull and mandible. Moreover, a 3D biomechanical model was used to explore the functional consequences of the observed patterns of co-variation. Our results show the efficiency of the method in investigations of complex morpho-functional patterns. Indeed, the description of shape co-variation between the skull and the mandible highlighted the location and the intensity of their functional relationships through the jaw adductor muscles linking these two structures. Our results also demonstrated that shape co-variation in form between the skull and mandible has direct functional consequences on the recruitment of muscles during biting.

Combined finite element and multibody dynamics analysis of biting in a Uromastyx hardwickii lizard skull

Lizard skulls vary greatly in shape and construction, and radical changes in skull form during evolution have made this an intriguing subject of research. The mechanics of feeding have surely been affected by this change in skull form, but whether this is the driving force behind the change is the underlying question that we are aiming to address in a programme of research. Here we have implemented a combined finite element analysis (FEA) and multibody dynamics analysis (MDA) to assess skull biomechanics during biting. A skull of Uromastyx hardwickii was assessed in the present study, where loading data (such as muscle force, bite force and joint reaction) for a biting cycle were obtained from an MDA and applied to load a finite element model. Fifty load steps corresponding to bilateral biting towards the front, middle and back of the dentition were implemented. Our results show the importance of performing MDA as a preliminary step to FEA, and provide an insight into the variation of stress during biting. Our findings show that higher stress occurs in regions where cranial sutures are located in functioning skulls, and as such support the hypothesis that sutures may play a pivotal role in relieving stress and producing a more uniform pattern of stress distribution across the skull. Additionally, we demonstrate how varying bite point affects stress distributions and relate stress distributions to the evolution of metakinesis in the amniote skull.